1. Field of the Invention
This invention relates to a radiation detector, an X-ray CT apparatus, and a method for manufacturing a radiation detector.
2. Background Art
In an X-ray CT (computer tomography) apparatus, a solid-state detector (hereinafter referred to as a radiation detector) based on a scintillator is used to increase the number of detection points to improve spatial resolution.
The radiation detection unit provided in this radiation detector includes numerous photoelectric conversion elements partitioned on a substrate and scintillators laminated thereon. The scintillators, which correspond to respective detection compartments of the photoelectric conversion elements, are separated and partitioned by grooves. Furthermore, the radiation detection unit includes collimator plates, which control X-ray radiation incident on the individual scintillators and absorb scattered radiation to reduce crosstalk due to the scattered radiation.
To meet the demand for rapid and high-definition photographing in a wide area, JP-A-2001-120539 (Kokai), for example, proposes a technique of using a multi-slice detector including a plurality of radiation detection units in the slice direction to also make efficient use of cone beams, that is, the spread angle (cone angle) of X-ray radiation in the slice direction.
However, the technique disclosed in JP-A-2001-120539 (Kokai) does not take into consideration the effect of temperature variation. Hence, for example, the linear expansion coefficient is different between the substrate with the photoelectric conversion elements provided thereon and the base plate to which the substrate is attached. Thus, a difference occurs in the amount of thermal expansion or shrinkage, which may cause a gap between the radiation detection units and/or destroy the substrate with the photoelectric conversion elements provided thereon, for example. As the number of radiation detection units disposed in the slice direction increases, the effect of temperature variation may increase.